Process for the preparation of ammonium nitrate



Prebeafgr- Jan. s, 1935. G FAUSER 1,987,552

PROCESS FOR THE PREPARATION OF AMMONIUM NITRATE Filed May 21, 1931 mousse FOB mmm o Farmer Nome, Etaiy, seals-nor to Montecatini, Societa Generals per liindustria immeraria Ed Agric 0.9!!! or Application 21, 1$l1,-eristl No. 5359,1632

' in Ready June 2, 193i? The commercial preparation of ammonium nitrate has been heretofore carried out by saturating nitric acid with ammonia in intensely cooled apparatus in order to avoid a temperature in- 5 crease in the acid during the reaction.

I is resorted to may be explained bythe fact that The reason for such a cooling lim in the fact that the boiling temperature oi nitric acid is lower than that of an ammonium nitrate solution, so that it would not be practicable to increase the heat of reaction in order to evaporate the mother liquor or the solution, as is practised, on the contrary, in the preparation of onium sulphate.

A further reason why an intense coolingoi the ammonium nitrate saturators during the reaction such apparatus is quickly corroded by 1 g nitric acid solutions.

However, the elimination oi the heat generated by the reaction between nitric acid and ammo by means of cooling water represents an irra tional operation, since the ammonium nitrate solution obtained in that way is very much diluted, and in order to get the dry salt therefrom it is necessary to subsequently submit the said solution to a concentration requiring a considerable expense of heat or steam.

The present invention provides a simple means of obviating the above dimculties, i; w. as it permits the utilisation of the heat 0! rwction in order to concentrate the onium nitrate solu tion without incurring the loss of nitric acid and ammoma.

The invention essentially consists in out the reaction between nitric acid and in monia in a receptacle or container at a higher pressure than that correspondingte the vapor tension of the ammonium nitrate solution obtained, at the temperature resulting tram the reaction. This solution is subsequently into another receptacle at atmospheric pressure or, better, at a reduced pressure, and is evaporated through the heat developed by the reaction itself.

A diagram of the process is shown in the accompanying drawing, it being understood however that the invention is not limited to the details shown.

The nitric acid and ammonia are drawn by the pumps A and B respectively and conveyed, in the proportions requisite for the reaction, into the coils C and D where they are preheated by means is, I, a joint-stock the temperature rises up to I'm-180 C. However no nitric vapours can develop since a higher pressure is maintained than that corresponding to the vapor tension of the resulting solution at the temperature produced by the reaction.

In order to avoid corrosion of the metal sur= i'ace oi the receptacle, it is advisable to provide a slight excess oi ammonia over the stoichiometrlc proportions required by the reaction, so as to render the ammonium nitrate solution "alkaline;

The pressure inside of the reaction chamber E is maintained constant by means oi an automatic valve 5, which permits the err-1;- nitrate solution continuously to discharge itself into the outer vessel G, this vessel being at atmospheric pressure or, better, below atmospheric pressure. The liquid in contact with the inner vessel is heated to ebullition, and the concentrated ammonium nitrate solution is led ofi by the pipe H, whilst the steam developing from the solution is conveyed by the pipe I to the rectifying column The duty oi this col is to separate the mall amount of ammonia present in the wet steam, and at the same time to preheat the nitric acid and ammonia passing to the saturator for reaction. The extracted water is disced through the siphon it, where the cute is recovered through the pipe P, returned to the cycle.

' Having now particularly described and ascentained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is:-:

i. The process of preparing a concentratedso lution of onium nitrate which comprises is, acting onia with asolution of nitric acid ina container ate pressure greater than the vapor tension of the resulting solution of sun monium nitrate at the temperature produced by the reaction, passing said solution oi-onium nitrate into a second container surrounding said first container at a pressure inferior to that oi the first container, and evaporating the water in said last-mentioned solution by the heat senerated in said first container.

2. The process of preparing a concentrated so= lution of ammonium nitrate which comp re acting ammonia with a solution of nitric acid at a pressure greater than the vapor tension at the resulting solution of ammonium nitrate at th temperature produced' by the reaction, oil? said solution of ammonium nitrate, and con centrating said last-mentioned solution. by the evaporation thereof,. at a pr 1; at which said reaction is at which said reaction is effected, by the heat o! the reaction oi. the ammonia with the nitric acid solution.

3. The process 01' preparing a concentrated solution oi ammonium nitrate which comprises pumping ammonia and a solution of nitric acid through separate coils disposed in a container, mixing and reacting said ammonia with said solution of nitric acid at a pressure greater than the vapor tension 01' the resulting solution of ammonium nitrate at the temperature produced by the reaction, passing oi! said solution 0! ammonium nitrate, evaporating said last-mentioned solution, at a pressure lower than that at which said reaction is cheated, by the heat of the reaction of the ammonia with the nitric acid solution, and leading said last-mentioned vapor products to said container to effect a preliminary heating of the ammonia and nitric acid solution passing through the coils disposed in said container.

4. The process of preparing a concentrated solution of ammonium nitrate which comprises pumping ammonia and a solution of nitric acid through separate coils disposedin a rectifying column, mixing and reacting said ammonia with said solution of nitric acid in a container at a line and thus avoid the corrosion of the metal surfaces of the container, passing 01! said solution of ammonium nitrate, evaporating said lastmentioned solution, at a pressure interior to that 01' the reaction of the ammonia with the nitric acid solution, leading said last-mentioned vapor products to said rectifying column to elect a preliminary heating of the ammonia and nitric acid solution passing through the coils disposed in said rectifying column and to separate the excess ammonia from the water vapor for repeated utilization,

5. The process of preparing a concentrated solution of ammonium nitrate which mixing and reacting ammonia with-a calm on of 10 nitric acid in a container at a pressure greater than the vapor tension of the resulting solution of ammonium nitrate at the temperature produced by the reaction, passing said solution of ammonium nitrate into a second container surrounding said first container at a pressure inter- .rior to that of the first container and interior to atmospheric pressure, and evaporating the water in said last-mentioned solution by the heat generated in said first container.

so 6. The process or preparing a concentrated solution of ammonium nitrate,'which comprises continuously pumping ammonia and a solution of nitric acid through separate tubing! into a container, where they are mixed and reacted; main- 3' taining a pressure in said container greater than the vapor. tension oi the resulting solution oi! ammonium nitrate at the temperature produced by the reaction, while continuously passing oi! said solution of ammonium nitrate irom said tion of concentrated ammonium nitrate thus pre- 35 GIACOMO PAUSIR. 

